1. Field of the Invention.
This patent deals with the decolorization of glycosides which are useful as surfactants and for other purposes.
2. Description of the Art.
Glycosides are known to have several uses including their incorporation into detergent products as nonionic surfactants. Lower glycosides, that is those materials having a short hydrophobic moiety attached to the saccharide backbone as later described, are useful as intermediates for manufacturing higher glycosides. The lower glycosides are also useful for such purposes as mold release agents, for polymers which require a hydroxyl functionality, and as a formaldehyde scavenger in various products which utilize formaldehyde as a reactant.
Glycosides are typically formed from a lower saccharide which may be either monomeric or polymeric with regard to the saccharide unit. For reasons which are not fully understood the glycosides obtained from most processes are dark colored. The color ranges from dark yellow to coffee black depending upon the conditions under which the glycoside is produced. The color is not inherent to the glycoside per se but rather to the presence of humins which are co-produced with the glycoside.
It has been suggested that the color bodies (humins) in the glycoside composition may be removed by adsorption with resinous components. This process requires that the entire glycoside composition be mixed with a resin in sufficient volume to substantially remove the color forming materials.
It has also been suggested that the color bodies present in a glycoside composition may be eliminated by treatment with various reducing acids. The acid reduction has its limitations in that the acidic material must be neutralized or removed from the end products. This is the case with laundry detergents. Typically laundry detergent products are formulated in the alkaline pH range to facilitate removal of body soil. Thus while there is some market for glycosides in the acid pH range it is desired not to incorporate any more acid than is necessary. For a description of the use of reducing acids to produce glycosides see European Patent Application No. 82305286.5 to Arnaudis published as 0 077 167 on April 20, 1983.
Further discussion of treating a glycoside composition to reduce color is found in European Patent Application No. 83200572.2 to Mao published as 0 092 875 on November 2, 1983. In Mao the acid catalyst employed is stated to be destroyed after at least 90% of the short chain alkyl monosaccharide (glycoside) has been destroyed and before the average polysaccharide chain length exceeds about 20. U.S. Pat. No. 4,393,203 to Leslie issued July 12, 1983 describes the treatment of glycosides with a wipe film evaporator to assist in color reduction. Rau in U.S. Pat. No. 4,465,828 issued August 14, 1984 suggests using hydroxy carboxylic acids to minimize color formation when preparing glycosides.
A general method of preparing glycosides is found in U.S. Pat. No. 3,219,656 to Boettner issued November 23, 1965. Descriptions of producing alkyl glycosides are also found in U.S. Pat. No. 3,547,828 to Mansfield issued December 15, 1970 and U.S. Pat. No. 3,598,865 to Lew issued August 10, 1971. Roth also describes the preparation of glycosides in U.S. Pat. No. 4,223,129 issued September 16, 1980.
It is also known that glycosides may be decolorized by using a bleaching material. Suitable bleaches include materials such as hydrogen peroxide for bleaching. It has been observed, however, that upon exposure to high temperature, a bleached glycoside product can revert to a darker color product upon standing.
Hydrogenation of saccharides to form polyols has been known as evidenced by Kool in U.S. Pat. No. 2,609,399 issued September 2, 1952. It is not the intent of the present invention to form polyols by hydrogenation as this destroys the ketone and aldehyde functionality desired for glycoside formation.
It has now been discovered that the catalytic hydrogenation of a glycoside composition can substantially reduce the color. The hydrogenation of the glycoside composition of the present invention allows for considerably greater stability after color removal than does bleaching. That is, the hydrogenation of the color forming bodies in the glycoside composition leads to a more stable product than does the bleaching which gives products capable of reversible reactions.
Throughout the specification and claims percentages and ratios are by weight, temperatures are degrees Celsius and pressures are in KPascals unless otherwise indicated. To the extent that any of the references mentioned in this application are applicable to the present invention they are herein incorporated by reference.